[jboss-user] [JBoss Seam] - No concurrent calls on stateful bean!

[toni]

Hi,

if I send many simultaneous HTTP requests to my seam application, which carry out a particular action, then I get an exception.

To reproduce this I have create a short test application, which you find below.

The test application exists of a JSF Table, which displays a set of entities. Each entity bean can be deleted by clicking on a "delete" link. 

If I delete the entity beans sequentially, then everything works correctly. However, if I very quickly click on many links, then sometimes I get the following exception:

Caused by: javax.ejb.ConcurrentAccessException: no concurrent calls on stateful bean 'jboss.j2ee:service=EJB3,name=TemplateAction' (EJB3 4.3.13) at org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulInstanceInterceptor.java:73)

I read of course, that this happens for reentrant calls on beans (A->B->A) or when one starts a thread inside a EJB, but that's not what I'm doing.

I already upgraded to SEAM 1.1, because I thought might/could be a bug. But I guess it's my lack of understanding.

To reproduce the error, I have create the following example, so that people here can reproduce the error. Just copy and paste the source code it into an existing project and call "/test.seam". 

It takes only 3-4 minutes. I appreciate any comments and help.

Toni


Test.java
-------------
@Entity
@Name("test")

public class Test
{
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  long id;

  String testText;

  public long getId()
  {
    return id;
  }

  public void setId(long id)
  {
    this.id = id;
  }

  public String getTestText()
  {
    return testText;
  }

  public void setTestText(String testText)
  {
    this.testText = testText;
  }
}


BasicTest.java
---------------------
@Local
public interface BasicTest
{
  public String list();

  public String create();

  public String select();

  public String save();

  public String delete();

  public void destroy();

  public DataModel getDataModel();
}


TestAction.java
------------------------
@Name("testAction")
@Stateful

public class TestAction implements BasicTest
{
  @In(create = true)
  EntityManager entityManager;

  @In(create = true)
  @Out
  @Valid
  Test test;

  @Out(required = false)
  DataModel dataModel;

  @Begin(join = true)
  public DataModel getDataModel()
  {
    if (dataModel == null)
      dataModel = new ListDataModel();
    dataModel.setWrappedData(entityManager.createQuery("from Test").getResultList());
    return dataModel;
  }

  @Begin(join = true)
  public String list()
  {
    return "tests";
  }

  public String create()
  {
    test = new Test();
    return "test";
  }

  public String select()
  {
    test = (Test) dataModel.getRowData();
    return "test";
  }

  @End
  public String save()
  {
    entityManager.merge(test);
    return "tests";
  }

  @End
  public String delete()
  {
    entityManager.remove(dataModel.getRowData());
    return "tests";
  }

  @Destroy
  @Remove
  public void destroy()
  {
  }
}


----------- test.jsp --------------

<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<%@ taglib uri="http://jboss.com/products/seam/taglib" prefix="s" %>

<f:view>

  <h:form>
    <s:validateAll>

      <h:panelGrid columns="1">

        <h:outputText value="Type"/>
        <h:inputText size="20" value="#{test.testText}"/>

      </h:panelGrid>

      <h:messages/>
      <h:commandButton type="submit" value="Save" action="#{testAction.save}"/>

    </s:validateAll>
  </h:form>

</f:view>




----------- tests.jsp ----------------------

<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<%@ taglib uri="http://jboss.com/products/seam/taglib" prefix="s" %>

<f:view>


  <h:form>
    <h:outputText value="No Test Entities available" rendered="#{testAction.dataModel.rowCount == 0}"/>

    <h:dataTable value="#{testAction.dataModel}" var="t" rendered="#{testAction.dataModel.rowCount > 0}">

      <h:column>
        <f:facet name="header">
          <h:outputText value="Type"/>
        </f:facet>
        <h:outputText value="#{t.testText}"/>
      </h:column>

      <h:column>
        <f:facet name="header">
          <h:outputText value="Action"/>
        </f:facet>
        <h:commandLink value="delete" action="#{testAction.delete}"/>
      </h:column>

    </h:dataTable>

  </h:form>

  <h:outputLink value="test.seam">
    <f:param name="conversationId" value="#{conversation.id}"/>
    <h:outputText value="Create Another Test Entity"/>
  </h:outputLink>

</f:view>





-------------- add to faces config ---------------------

    <navigation-rule>
    <navigation-case>
      <from-outcome>tests</from-outcome>
      <to-view-id>/tests.jsp</to-view-id>
    </navigation-case>
    <navigation-case>
      <from-outcome>test</from-outcome>
      <to-view-id>/test.jsp</to-view-id>
    </navigation-case>
  </navigation-rule>

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